You will learn more from tearing into your piece and making it right than you will from deciding it's finished while it's still not right. It's HARD and FRUSTRATING (and sometimes terrifying!) to tear in to what looks like a nice piece, but the results will be so much better after you've done it - believe me, I've cut off noses to build heads longer or shorter, I've cut all the way down to the armature to redo something, I've lifted more tails than I can count when they wound up too low, I've ripped out eyes and re-positioned them over and over and over on the same piece to get them right from every angle. Remodeling the piece is PRACTICE which helps you get it perfect, and helps you learn how to make the next piece better in less time.
I was working on "Just Trying to Help" (below) in my booth at Equine Affaire in Mass. a few years ago when I realized her neck was WAAAY too long. Since I'm used to building adult horses, I'd given her an adult neck - and a lovely one it was, too. Her head was PERFECT for a foal, but that neck had to be shortened, so I cut the neck behind her head, declared "OFF with her head!" and ripped it off, resulting in a *gasp* from the dozen or so people standing behind me who I hadn't noticed. I cut about an inch out of her neck, cut off the excess armature wire and put her head back in place. After working for a while longer, I grumbled, "I'm going to have to cut her head off again," speaking to myself. A woman who was browsing questioned me about it and stayed for over an hour waiting for me to actually do it. When I finished what I was working on and was ready to deal with her neck again, I cut her neck right behind her head, declared, "OFF with her head!" with an evil chuckle, and heard more gasps. But as you can see from the bronze below, cutting her neck shorter was the right thing to do, despite the fact it was beautifully detailed and perfect - it was just too long. Her head was perfect too, but I had to yank it off and chance ruining it to get to that neck and armature wire.
My point is, don't fall in love with your pieces while working on them. You have to be ruthless with your work, cutting, pushing, pulling, doing whatever is necessary to get the piece to be what you want, not just what it winds up being. You will learn more from "killing your darlings" and reworking them than you will from just letting something go because it's "good enough." Never stop pushing yourself! Kill your darlings and learn from the process!